Temporarily revert "[PowerPC] Allow tail calls of fastcc functions from C CallingConv functions."

It is causing sanitizer failures on llvm tests in a bootstrapped compiler. No bot link since it's currently down, but following up to get the bot up.

This reverts commit r319218.

llvm-svn: 320106

2 files changed, 8 insertions, 13 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index f885127e6aa..3fe9fe73499 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -4397,18 +4397,13 @@ hasSameArgumentList(const Function *CallerFn, ImmutableCallSite CS) {
 static bool
 areCallingConvEligibleForTCO_64SVR4(CallingConv::ID CallerCC,
                                     CallingConv::ID CalleeCC) {
-  // tail calls are possible with fastcc and ccc.
-  auto isTailCallableCC  = [] (CallingConv::ID CC){
-      return  CC == CallingConv::C || CC == CallingConv::Fast;
-  };
-  if (!isTailCallableCC(CallerCC) || !isTailCallableCC(CalleeCC))
+  // Tail or Sibling call optimization (TCO/SCO) needs callee and caller to
+  // have the same calling convention.
+  if (CallerCC != CalleeCC)
     return false;
 
-  // We can safely tail call both fastcc and ccc callees from a c calling
-  // convention caller. If the caller is fastcc, we may have less stack space
-  // then a non-fastcc caller with the same signature so disable tail-calls in
-  // that case.
-  return CallerCC == CallingConv::C || CallerCC == CalleeCC;
+  // Tail or Sibling calls can be done with fastcc/ccc.
+  return (CallerCC == CallingConv::Fast || CallerCC == CallingConv::C);
 }
 
 bool
diff --git a/llvm/test/CodeGen/PowerPC/duplicate-returns-for-tailcall.ll b/llvm/test/CodeGen/PowerPC/duplicate-returns-for-tailcall.ll
index 9c0e77dafde..520efd8106f 100644
--- a/llvm/test/CodeGen/PowerPC/duplicate-returns-for-tailcall.ll
+++ b/llvm/test/CodeGen/PowerPC/duplicate-returns-for-tailcall.ll
@@ -42,10 +42,10 @@ if.end4:                                          ; preds = %if.end
 if.then6:                                         ; preds = %if.end4
   %call7 = tail call fastcc signext i32 @call3(i32 signext %a, i32 signext %b, i32 signext %c)
   br label %return
-; tail calling a fastcc function from a ccc function is supported.
+; No duplication here because the calling convention mismatch means we won't tail-call
 ; CHECK_LABEL: if.then13:
-; CHECK:       %[[T2:[a-zA-Z0-9]+]] = tail call fastcc signext i32 @call3
-; CHECK-NEXT:  ret i32 %[[T2]]
+; CHECK:       tail call fastcc signext i32 @call3
+; CHECK-NEXT:  br
 
 return:                                           ; preds = %if.end4, %if.then6, %if.then2, %if.then
   %retval.0 = phi i32 [ %call, %if.then ], [ %call3, %if.then2 ], [ %call7, %if.then6 ], [ %c, %if.end4 ]